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Homework Help: Velocity of cart after seperation

  1. Feb 12, 2013 #1
    1. The problem statement, all variables and given/known data
    Hello, so i had a family party and my cousin was doing his physics homework so i decided to join in. now i'm at home and was playing with one of the problems that his teacher didn't assign and got an answer that i want to check because my teacher skipped the moment chapter(i go to community college and we ran out of time because we had a strike) so i really want to know if i got it.

    i can't remember what exactly the question said but i remember my sketch

    cart 1 and cart 2 are connected as a train going 4m/s

    [m1]- *break* -[m2]-->7m/s
    cart 1 cart 2
    what is the velocity of cart 1

    2. Relevant equations

    3. The attempt at a solution
    P = mv

    p=p' because of conservation of momentum?

    p = m1v1 + m2v2
    v1 = (p - m2v2)/m1
    this is where i'm kind of iffy... if together they go 4m/s does that mean they both go 4m/s or is it divided by 2 each?
  2. jcsd
  3. Feb 12, 2013 #2
    now i'm thinking... if i need a ratio between the two masses?
  4. Feb 12, 2013 #3
    okay i just realized i use v2=7m/s for v1= (p - m2v2)/m1... lol
    Last edited: Feb 12, 2013
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